Cage of Eden manga volume 11 features story and art by Yoshinobu Yamada.

Akira and the others finally reach the mysterious structure towering over the jungle below. Though they're thrilled to discover the first clearly man-made artifact they've found in this world, Eiken is nowhere to be found! Instead, all they find is his luggage... an ominous sign to say the least in a landscape full of savage predators!